Sudden Death in Patients With Chronic Bifascicular Block

ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities

“…Syncope is common in patients with bifascicular block. Although syncope may be recurrent, it is not associated with an increased incidence of sudden death (73,(102)(103)(104)(105)(106)(107)(108)(109)(110)(111)(112). Even though pacing relieves the neurological symptoms, it does not reduce the occurrence of sudden death (108).…”

“…There is convincing evidence that in the presence of permanent or transient third-degree AV block, syncope is associated with an increased incidence of sudden death regardless of the results of the electrophysiological study (64,114,115). Finally, if the cause of syncope in the presence of bifascicular block cannot be determined with certainty, or if treatments used (such as drugs) may exacerbate AV block, prophylactic permanent pacing is indicated, especially if syncope may have been due to transient third-degree AV block (102)(103)(104)(105)(106)(107)(108)(109)(110)(111)(112)116).…”

Dispersion in Ventricular Repolarization in Patients with Severe Intraventricular Conduction Disturbances

“…This latter point is particularly important since most previous invasive studies on asymptomatic patients with BFB have not included programmed stimulation for provocation of ventricular arrhythmias, although a high risk for sudden death, presumably due to ventricular arrhythmias, has been recognized for a long time. [28][29][30][31] The assessment of refractory periods alone does not provide a complete picture of relevant electrophysiological factors for the induction of ventricular arrhythmia by programmed stimulation in the RV. 23,42,43 Thus, Yuan et al 23 observed that repolarization time (the sum of activation time and action potential duration) could be pseudonormal in the presence of significant dispersion of activation time due to a relatively shortened monophasic action potential.…”

“…13 Previous observations suggest that the susceptibility to spontaneous or inducible polymorphic ventricular arrhythmia, is related to an increased dispersion of refractoriness, while monomorphic ventricular tachycardia (VT) is related to increased dispersion of activation time (conduction velocity). 22,24,26,27 Patients with bifascicular block (BFB) (as defined below) are relatively common (1%-1.5% of the population $ 35 years) and have a high cardiovascular mortality, including an increased risk of sudden death, [28][29][30][31] which makes it important to identify prognostic instruments for suitable therapeutic interventions. Prolonged total activation time is by definition a salient feature in this high risk patient population, and regional differences in activation time result from the spread of impulses via the specialized Purkinje fibers in some regions and via cell-to-cell connections between ordinary myocardial cells in others.…”

Long‐term prognosis in patients with bifascicular block – the predictive value of noninvasive and invasive assessment

“…Furthermore, the largest survival benefit of implantable cardioverter‐defibrillator (ICD) therapy in the MADIT II study was observed in patients with IVCD [2]. Although a majority of such patients have structural heart disease and impaired myocardial function [3–7], a decision of whether or not to treat patients within this group with an ICD and/or cardiac resynchronization therapy (CRT) cannot be made on a general basis. High‐risk individuals must be identified in order to obtain an optimal cost‐benefit (risk‐benefit) relation.…”